This invention relates to a novel photosensitive member for inputting digital light which is utilized in the art of electrophotography, and more particularly a photosensitive member which can satisfy various requests regarding digital recording which are increasing with year. A prior art photosensitive member utilizing a specific flow pattern of photo-current in a thin photosensitive layer, formed by binding fine photoconductive crystals of a small particle diameter with a highly insulative binder, has not been utilized commercially for inputting digital light.
Photosensitive members utilized in the prior art method of electro-photography were simple photoconductors or photoconductors resembling them. In U.S. Pat. No. 2,297,691 to Carlson, photosensitive members made of sulfur, anthracene, anthraquinone, melted mixture of sulfur and selenium or anthracene, etc. are disclosed. In recent years, photosensitive members including a photosensitive layer made up of amorphous Se, or amorphous silicon or a bonded layer of ZnO prepared to have characteristics similar to that of the amorphous Se layer has been used. More particularly, a photosensitive layer of the so-called function separation type utilizing organic semiconductors has been developed in recent years.
The inventor has invented a series of the methods of electrophotography utilizing a photosensitive member comprising a combination of a highly insulative film and a photosensitive layer. All of the prior art methods of electrophotography were developed based on analogue theory, and efforts have been made to cause so-called .gamma. characteristic to approach that of the film used in the silver chloride photographic technique. As a consequence, materials which were selected such that photocurrent proportional to the quantity of incident light would flow have been used as a rule. For this reason, photosensitive members utilizing above mentioned amorphous Se layer or the like have been used.
Consequently, the photosensitive member based on the analogue concept and utilized in the prior art methods of electrophotography is not suitable for use in electrophotography which operates digitally in view of the .gamma. characteristic of the latent image. In the digitally operating devices are included computer output devices, copy machines in which a picture image is processed after digital decomposition, and any other digital machines. Accordingly, in the art of electrophotography, provision of a photosensitive member capable of utilizing digitally operating electrophotography has strongly been desired.